Synthesis and characterization of pentablock copolymers based on Pluronic® L64 and poly(methyl methacrylate)

The synthesis and characterization of amphiphilic pentablock copolymers based on Pluronic® L64 (PEO₁₃-PPO₃₀-PEO₁₃) and poly(methyl methacrylate) (PMMA), synthesized via atom transfer radical polymerization (ATRP) is reported. The L64 is first transformed into a bifunctional ATRP macroinitiator which was subsequently chain extended with MMA by ATRP to afford PMMA-b-L64-b-PMMA pentablock copolymers. The chemical structure of the synthesized amphiphilic block copolymers is characterized by FTIR, ¹H NMR spectroscopy, and gel permeation chromatography (GPC). The GPC profiles of the block copolymers clearly show an increase in molar mass after the ATRP of MMA and monomodal molecular weight distributions for all the samples. Finally, preliminary studies on their aggregation behavior in aqueous solution have also been investigated by measuring the scattering light intensity as function of block copolymer concentration to estimate the critical aggregation concentration (CAC). The CAC decreases with increasing of hydrophobic content in copolymer, i.e., ∼25 and ∼15 mg/mL, respectively, is estimated for the pure L64 and PMMA₁₃-b-L64-b-PMMA₁₃. Further, with increase in temperature, the CAC is found to decrease that is attributed to the dehydration of the PEO segments at higher temperatures.